For the regulation of calcium and phosphate metabolism in the animal or human and for the regulation of normal bone growth, development and maintenance, the metabolites of vitamin D are essential agents. In the normal animal or human, these bone-related processes are regulated by 1.alpha.,25-dihydroxyvitamin D.sub.3, a metabolite formed from vitamin D.sub.3 by hydroxylation at carbon 25 and then at carbon 1. This discovery has stimulated much activity aimed at preparing the natural metabolite and structural analogs thereof. Results of these efforts are summarized in several reviews (e.g. Yakhimovich, Russian Chem. Rev. 49, 371 (1980); DeLuca et. al. Topics in Current Chemistry, Vol. 83, p. 1 (1979); Ann. Rev. Biochem. 52, 411 (1983)). Important examples of synthetic analogs of the natural hormone include 1.alpha.-hydroxyvitamin D.sub.3 (U.S. Pat. No. 3,741,996), 1.alpha.-hydroxyvitamin D.sub.2 (U.S. Pat. No. 3,907,843), 3-deoxy-1.alpha.,25-dihydroxyvitamin D.sub.3 (U.S. Pat. No. 4,264,512), 10,19-dihydro-1.alpha.-hydroxyvitamin D.sub.3 compounds (U.S. Pat. No. 4,159,326), 1.alpha.,24-dihydroxyvitamin D.sub.3 (U.S. Pat. No. 4,022,891), 24,24-difluoro-1.alpha.,25-dihydroxyvitamin D.sub.3 (U.S. Pat. Nos. 4,226,788, 4,284,577), 26,26,26,27,27,27-hexafluoro-1.alpha.,25-dihydroxyvitamin D.sub.3 (U.s. Pat. No. 4,358,406) and other side-chain or ring A fluoro analogs (U.S. Pat. Nos. 4,069,321; 4,224,230; 4,307,025).